Notes on the Genus Taphrina

Notes on the Genus Taphrina. BY BENJAMIN L. ROBINSON. URING the winter of 1886-7 I had an opportunity to D study, from dried and alcoholic material, a number of American and European species of the genus Taphrina. As the literature of the group, particularly on the American forms, is rather scanty, the notes which I have been able to make may be of assistance to those who wish to continue the study of this interesting group. In the systematic examina- tion of European species much valuable aid has been derived from the papers of Sadebeck1 and of Johanson8. These writers, it will be noticed, differ in the names they retain for the group; and a brief explanation of the synonymy of the genus will not be out of place. The species, combined by Sadebeck, in 1883, into a single genus, were formerly classed in three closely related genera, Taphrina, Fries, Ascomyces, Mont, et Desm., and Exoascus, Fuckel. Of these genera the first is the oldest, having been described by Fries as early as 1815 under the name of Taphria, which, to avoid possible confusion with an insect genus, was in 1825 altered to Taphrina. In his paper just mentioned Sadebeck has preferred, although without stating his reasons, to retain for the combined genus the youngest of the three names, that of Exoascus, Fuckel. Johanson agrees with Sadebeck in thinking that all the species should be combined into a single genus, but, seemingly with much 1 Untersuchnngen iiber die Piligattung Exoascus, in Jahresbuch der wissenschaft- lichen Anatalten, Hamburg, 1883, PP- 93~I34- ' Om Svampslagtet Taphrina, in Ofversigt af Kongl. Vetenskaps-Akademiens Forhandlinger, 1885, Stockholm, N: o I, pp. 39-47. [ Anna1» of Botany, VoL L No. n. November 1887.] > Downloaded from https://academic.oup.com/aob/article-abstract/os-1/2/163/132381 by St Francis Xavier University user on 17 August 2018 164 Robinson.—Notes on the Genus Taphrina. more regard for the rules of priority in nomenclature, retains the name Taphrina of Fries. There appears to be all the more reason for this from the fact that, as early as 1866, Tulasne1 revised the genus of Fries and expanded its limits so that it might take in all the species then known of Ascomyces and Exoascus, thus using the name Taphrina, so far as the knowledge of the time enabled him, in the same sense as it is at present employed. From these considerations it seems best to follow Johanson in calling the group' Taphrina, Fries, char, a Tulasne emend.,' a sort of nomenclature which, if not brief, is yet in accord with priority, and incapable of being misunderstood. The members of this genus are in structure among the simplest of the Ascomycetes, and in them no trace of sexual function has yet been found. They present also some features of similarity to the Saccharomycetes, to which group there seems a growing tendency to consider them closely related2. With one possible exception, all the species known are parasitic in their habit. They seldom attack herbs, but are commonly found on shrubs or trees, especially those of the Rosaceae, whence the chief economic importance of their study. Their mycelia penetrate the tissues of the host to various depths where, in some species at least, they pass the winter. In the spring they begin their development anew, and enter the young shoots and leafy parts of the plant attacked ; here they spread their hyphae beneath the cuticle, or in some species just below the epidermis, forming a branching network. From this sort of hymenium the asci arise. They are more or less cylindrical in form, and usually occur in great numbers, densely packed together. They are found between the cuticle and epidermis, being developed in the species which have their hymenia beneath the epidermis, as enlarged ends of vertical threads which, 1 Super Friesians Taphrinamm Genere, in Ann. des Sciences nat., sei. 5, Tome v, 1866, p. 133. s See De Bary, Vergl. Morph. und Biol. der Pilze, Mycetozoen nnd Bacterien, Leipzig, 1884, pp. 386-394. Downloaded from https://academic.oup.com/aob/article-abstract/os-1/2/163/132381 by St Francis Xavier University user on 17 August 2018 Robinson.—Notes on the Genus Taphrina. 165 arising from the subepidermal network, make their way between the cells of the epidermis and become developed into asci which, as in the other species, are formed between the cuticle and epidermis. In several species each ascus is borne on a specialized portion of the mycelium known as the stalk-cell. These cells vary considerably in form, being sometimes long and slender, cylindrical or obconical, or, on the other hand, short and broad with flat and truncate bases. Within each ascus generally eight nearly spherical spores are formed, but the octosporic condition is often not permanent, for while yet in the ascus the spores divide by a process closely resembling the budding of the Saccharomycetes. In this way the asci frequently become filled with very numerous reproductive bodies, sometimes resembling the eight original spores, except in their smaller size and rather more oblong or oval form, in other cases becoming very minute and bacteria- like. The asci of several species are always polysporic at maturity, and no eight-spored condition is readily discernible in their development. Even in them, however, there seems reason to believe that the many-spored form is secondary, resulting from spore-division. As the asci grow they raise up the cuticle from the epidermis, and at some period, early in some cases, near maturity in others, break through to the surface. The release of the spores when the asci have not been subjected to any violent rupture, to which their delicate structure and superficial position render them liable, seems to be effected through a rather small orifice at the summit of the ascus. The presence of a Taphrina is manifested by the host in one or more of several ways: namely, by the occurrence on the leaves of roundish or irregular blotches, varying in colour from yellow to purple according to the species of the parasite; by. a curling or crisping of the leaves, sometimes accompanied by a toughening or cartilaginous modi- fication of the leaf-texture; by the swelling out of the softer parts of the leaves between the nerves, rendering the surface convex on one side and concave on the other; by deformity Downloaded from https://academic.oup.com/aob/article-abstract/os-1/2/163/132381 by St Francis Xavier University user on 17 August 2018 166 Robinson.—Notes on tlie Genus Taphrina of the fruit; and, lastly, by the swelling and distortion of the twigs and young branches. In showing in some degree the affinities within the group, as well as in furnishing a means of ready determination of the individual species here described, the following synopsis of the American species which I have been able to examine may be found useful. Tulasne, in subdividing his new genus, Taphriiia, had regard to the lines of division between the older genera of which it was composed, and accordingly grouped his species into those with so-called polysporic asci (Taphrina, Fries, and Ascomyces, Mont, et Desm.), and those with eight-spored asci (Exoascus, Fuckel). But, as just stated, the polysporic condition is probably secondary, and the spores of all the so-called octosporic species are very liable to multiply within the ascus. This distinction therefore does not seem of primary importance, and in arranging the American species it is better to follow Sadebeck and Joharison in grouping the species according to the depth to which their mycelia penetrate the tissues of the host-plant. It will be understood that the following synopsis is not intended to be exhaustive, as there are several forms of Taphrina more or less perfectly known in America which I have been unable to examine. SYNOPSIS OF AMERICAN SPECIES EXAMINED. I. Mycelium penetrating intercellularly the inner tissues of the host. (1) Fertile portion of the mycelium between the epidermis and the cuticle, (a) Asci raised on stalk-cells, T. Pruni (Fuckel), Tul. T. deformans (Berk.), Tul. (b) Asci without stalk-cells, T. purpurascens (Ellis et Evh.). (2) Fertile portion of the mycelium beneath the epidermis, T. PotentUlae (Fanv.), Johans. T.Jlava, Farw. Downloaded from https://academic.oup.com/aob/article-abstract/os-1/2/163/132381 by St Francis Xavier University user on 17 August 2018 Robinson.—Notes on the Genus Taphrina. 167 II. Mycelium spreading itself just below the cuticle, and not entering the tissues of the host. (a) Asci with stalk-cells, T. alnitorqua, Tul. (b) Asci without stalk-cells, T. aurea (Pers.), Fries. T. caerulescens (Mont, et Desm.), Tul. For Exoascus Wiesneri, Rathay, and Ascomyces Quercus, Cooke, see Taphrina deformans and T. caerulescens re- spectively. T. PRUNI (Fuckel), Tul. Exoascus Pruni, Fuckel, Ennumeratio Fungorum Nas- soviae, p. 29. This species occurs frequently in the United States upon Prunus domestka, L., and causes a peculiar hollow deformity of the fruit, the so-called 'plum-pocket' (Narren-Taschen). Late in June the infected plums reach almost their mature size, but consist merely of a thin shell having instead of pulp and stone only a few threads stretched irregularly across the cavity within. A Taphrina, probably identical with this, attacks several of our native species of Prunus, and has been found on P. maritima, Wang., Dartmouth, Mass., on P. virginiana, L., near Lake Willoughby, Vt, and on P. sero- tina, Ehr., Cambridge, Mass. On the last-mentioned host the fruit, which is normally nearly spherical, when infected becomes elongated or even somewhat spindle-shaped, and early attains a size several times greater than at normal maturity.

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